1. Field of the Invention
This invention relates generally to pipes that convey exhaust gases from an internal combustion engine, and more particularly to a pipe assembly for conveying exhaust gases that includes inner and outer pipes.
2. Description of the Related Art
Some existing exhaust manifold designs include a set of single-walled pipes emanating from an internal combustion engine and connected to downstream pipes. Significant noise is generated, however, when exhaust gases are conveyed from an internal combustion engine through a set of single-walled pipes emanating from the engine.
Single-walled pipes are susceptible to thermodynamic heat loss, which impedes operation of a catalytic converter, caused by the ambient atmosphere surrounding the single-walled pipe. Single-walled pipes are also easily damaged by impact, dirt, debris and corrosive substances. Because single-walled pipes suffer from the aforementioned and other shortcomings, there have been attempts to convey exhaust gases through double-walled pipes.
For example, in U.S. Pat. No. 4,022,019 to Garcea, two outer corrugated tubes are slipped over an inner smooth tube. The outer corrugated tubes insulate the inner tube, reducing heat transfer toward the outside atmosphere.
In U.S. Pat. No. 5,390,494 to Clegg, an inner pipe is surrounded by a thicker outer pipe. Corrugations in the inner pipe provide support during bending and reduce heat dissipation to the surrounding areas.
There continues to be a need, however, for new structural arrangements that reduce engine noise emitted by exhaust gas conduits while preventing heat dissipation from the exhaust gas conduits.